The sacrifice which causes sorrow to the doer of the sacrifice is no sacrifice. Real sacrifice lightens the mind of the doer and gives him a sense of peace and joy. The Buddha gave up the pleasures of life because they had become painful to him.
Our non-co-operation is with the system the English have established in India, with the material civilization and its attendant greed and exploitation of the weak.
An opponent is entitled to the same regard for his principles as we would expect others to have for ours. Non-violence demands that we should see every opportunity to win over opponents.
I do believe that, where there is only a choice between cowardice and violence, I would advise violence. I would rather have India resort to arms in order to defend her honour than that she should, in a cowardly manner, become or remain a helpless witness to her own dishonour. But I believe that nonviolence is infinitely superior to violence, forgiveness is more manly than punishment.